1. Field of the Invention
This invention is generally directed to methods and systems for integrity testing of seals associated with various packaging or containers and more specifically to a method and system for utilizing airborne or a combination of airborne and contact ultrasonic energy which is transmitted through a gaseous medium, such as air, to a seal from a transmitting transducer. A receiving transducer receives energy which either passes through the seal or is reflected therefrom and supplies signals to an analyzer or computer which provides output with respect to the seal integrity.
2. Brief Description of the Related Art
The non-contact, non-destructive and non-invasive inspection of the integrity of seals used in the packaging industry, and especially those used in packaging food, medical devices and pharmaceuticals, is becoming increasingly more important to ensure that the contents of packaged products remain suitable for use to thereby protect the health and welfare of consumers. In this respect, the industry provides for selectively testing of different product packaging including flexible pouches, trays, cups, blister packs, bottles and the like to ensure that the seals associated with such packages are free of faults or flaws. Such faults may be voids in a seal, inclusion of contaminants along a seal or closure, uneven and marginal heat seals, seals of insufficient size or width, delaminations in areas of a seal, and other seal characteristics associated with bonded materials utilized in the packaging industry.
There are numerous types of container filling and sealing machines currently used in the packaging industry. For example, vertical pouch filling and sealing machines are utilized to fill products through an opening in a top of the pouch afterwhich the pouch is sealed, cut and dropped onto a take away conveyor. Periodic or sequence testing of the seals is required to ensure that packages are free of contamination or faults.
Horizontal filling and sealing machines are used to either continuously move or periodically index packages which are filled from the top afterwhich a heat seal is provided using stationary or moving heat sealing jaws. The jaws may be associated with a heat sealing roller system. Seal testing is performed after sealing.
Certain type of pouches incorporate zipper or interlocking type closures which may be located adjacent to a heat seal. In order to prevent leakage, a zipper component on either side of the pouch is sealed by pressure and heat.
Form filled seal machines form a lower part of a package into a cavity and then load and fill a product into the package cavity and then seal a top layer onto the lower cavity or tray. This process is typically done in an indexing motion from one to several stations along a conveyor. The shape of the tray may be in-any form, however, most are rectangular, square or round.
Regardless of the type of product filling and sealing machines used, inspection of packages following filling and sealing is critical to ensure the integrity of the seals and thus the suitability of the packaged product for later use or consumption. Often, because packages are filled at high speed under critical conditions, a product may contaminate the area of a seal and thus interfere with an effective seal. Further, sealing tools can become contaminated, misadjusted or worn and can lead to the formation of bad or faulty seals during the packaging sealing process. In view of the foregoing, it is necessary to provide a method for inspecting and determining the integrity of packaging seals before product is shipped to consumers.
There are currently and in the industry a number of methods and devices for testing the integrity of seals associated with packages having different types of closures. The most basic testing procedure is through manual inspection of packaging, either visually, by touch, feel or destructive means. Manual inspection is suitable to determine obvious problems associated with packaging, such as a missing or partially applied lid, a separated seal, a ruptured or damaged container or closure and the like. Manual inspection, however, is not efficient, provides no variable data and is not effective to determine seal characteristics such as contaminations, voids in seals, delamination of seal layers, micro-holes or defects in a seal and like. To reduce costs while providing greater effectiveness in inspecting package seals, automated procedures and systems have been developed to inspect or test seals.
Such automated testing procedures have included the use of devices for applying pressure to packages which are carried along a conveyor. The degree of deflection of a package, or the amount of recovery a lid or wall of a package, after pressure is applied, is measured to determine whether or not leaks are present in either the packaging materials or in the seals associated therewith. Other types of physical tests include measuring package weight gain or loss, monitoring lid or closure deflection to determine if proper internal pressure is obtained and maintained in a package, the use of tracer gases such as a carbon dioxide, oxygen and helium, and electrical conductivity.
Other types of leak testing systems incorporate vacuum sources in differential and absolute pressure sensory systems. Packages are placed within chambers and vacuums are applied such as to create a differential pressure between an interior of a package and the surrounding vacuum chamber. Pressures within the testing chambers can be monitored so as to determine if there are changes in pressure after vacuums or partial vacuums are applied to thereby give an indication of a faulty seal or leak.
In U.S. Pat. No. 5,513,516 to Stauffer, A Method And Apparatus For Testing A Container System is disclosed which incorporates a vacuum chamber in which a flexible or semi-flexible package is cooperatively received. A flexible wall or membrane is provided within the testing chamber and designed to provide a sealing surface against a wall of the container. The use of the flexible wall or membrane allows inspection of packaging formed of gas permeable materials to be tested such that, during the testing process, pressure differentials are only due to leaks along the package seals, and not the packaging material.
Some of the problems associated with prior art pressure type testing chambers for use in the packaging industry to ensure the integrity of packaging seals is that the packages must be placed within a supporting chamber, afterwhich a change is made to the atmosphere surrounding the package seal. In instances where pressure is applied by mechanical force, leaks can be plugged or covered and contamination can occur to packages as well as cross-contamination between packages. Further, the number of steps necessary to complete a seal test limits the effective number of containers or packages which can be tested or inspected at any given period of time and potential leaks, plugged leaks or weak seals are not detectable.
A further type of automated and testing system uses ultrasonic energy which is directed through a package seal in a liquid medium, such as water. Sealed containers are placed in a testing apparatus where a liquid is used to ultrasonically couple an ultrasonic transmitter array and a receiver array to the container rim. Using such a system, the liquid must be introduced around the seal in order to allow ultrasonic energy to be effectively transmitted through the seal and be detected by the receiver array. Thereafter, the liquid must be drained off and the package removed from the apparatus. Because of the requirement for a liquid environment, such ultrasonic systems are considered destructive in most cases and have not proven to be efficient and adequate for testing with respect to many container seals.
One of the essential features of any testing method and apparatus is that it must be economical to the manufacturer to use so that the cost of products are not increased, such as by limiting production due to slow testing procedures. In light of the foregoing, there remains a need to provide an apparatus and procedure for testing package seals which incorporates testing procedures which facilitate the manner in which package seals can be inspected to ensure their integrity and wherein such testing procedures and apparatus can be used efficiently so that products can be tested rapidly along a product filling line without adversely effecting the overall economics of the packaging system.